1. Field of the Invention
The present invention relates to an airbag apparatus including an inflatable airbag for protecting a vehicle occupant In particular, the invention relates to an airbag apparatus further including a case for housing the airbag and an inflator, which case having a lid operable for exhausting inflation gas once filled inside the airbag.
2. Description of Related Art
Conventional airbag apparatuses are known, from US 2006/0066083 A1 and US 2006/0033316 A1, as each has an airbag inflatable with inflation gas, an inflator for supplying the inflation gas to the airbag, and a case for housing and holding the airbag and the inflator. The case includes a vent opening for allowing inflation gas inside the airbag to escape and a lid for closure of the vent opening and rotatable upon the operation of an actuator to open the vent opening.
In these apparatuses, the lids are configured to open the vent openings upon the activation of the actuator so inflation gas is released from the openings to reduce the internal pressure of the airbag in order that less reaction force is applied to a vehicle occupant by the airbag when the airbag inflated by the inflator receives the occupant.
In each of these apparatuses, the rotary shaft about which the lid opens is located at the end of the lid. That is, when the lid turns and opens around the rotary shaft, a leading end area of the lid facing away from the rotary shaft is separated away from the periphery of the vent opening orthogonally to the opening plane of the vent opening.
In order to secure good closing property, it is required that the entire outer edge of the lid is pressed onto the periphery of the vent opening on the outer side of the case. If the vent opening has a large opening area, it is difficult to impose the entire outer edge of the lid against the periphery of the vent opening in an even manner. Furthermore, if the vent opening has a large opening area, the lid has to be large as well. The large lid enlarges the turning radius of the lid, thereby enlarging the protrusion of the lid out of the case upon opening of the lid. In this case further measures have to be taken to prevent the lid from engaging surrounding parts of vehicle.